The interactions among salivary components, oral bacteria, and enamel surfaces are processes which are important for the initiation of a carious lesion. This study, an extension of our earlier work on dextran, proposes to focus on those salivary proteins which are capable of binding both hydroxyapatite and Streptococcus mutans. We plan to test quantitatively the protein bridge model for bacterial aggregation and also for Cellular adherence to a hydroxyapatite substrate. The technique of quasielastic laser light scattering will be used to determine the physical characteristics of the saliva fractions, the aggregation rates of the bacteria, and the concentration of bacteria that is bound to hydroxyapatite under different conditions including fluoride treatments. The specificity of the S. Mutans protein binding sites will be examined as well as the relationships between the protein characteristics and the effectiveness of the bridging mechanism.